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Tech Talk: Distinctness of Image
January 26, 2012
Distinctness of Image (DOI) is a measure of how crisp and sharply a reflected image appears. Learn about how DOI is measured, how it differs from gloss measurements, and its importance when evaluating floor finishes.
The most common description of the appearance of a flooring surface is gloss. However, using only gloss to describe a floor describes only a portion of how it will appear. Two floors may have an equal gloss but a very different appearance. To fully describe a floor, we need to consider more than just gloss.
What is gloss and how is it measured:
Gloss is a term used to describe the "shine" or light reflection of a flooring surface. Typical gloss meters measure gloss by projecting a beam of light onto the floor and measuring the amount of that light reflected back at the same angle within a /- 0.9 degree range. Because gloss readings are taken using a range, there will be variations of appearance between samples that give the same gloss reading. We could refine that range and get a better description. That measurement is called Peak Specular Reflectance.
What is Peak Specular Reflectance (RSpec):
RSpec is measured in the same way as gloss but uses a very tight range of /- 0.15 degrees. Two surfaces may have the same gloss reading but a greatly different RSpec. The higher the RSpec reading the more perfectly light is reflected. This reading gives a better indication of the floor appearance but can be further refined.
What is Distinctness of Image (DOI):
Distinctness of Image (DOI) is a measure of how crisp and sharply a reflected image appears. For example the ability to see a bright spot reflected in a floor as compared to being able to clearly see the outline of a light bulb or being able to read text in a reflected sign.
Distinctness of image is an indication of the perfection of a reflection and lack of haze or orange peel in a surface. The picture used at the top of this Tech Talk is an example of a floor with a very high Distinctness of Image. In effect, a high DOI measurement tells us that light is perfectly reflected and only small amounts of light are reflected in angles close to perfect (which would cause a fuzzy image). Due to advances in portable meters, DOI is now being used in the field to measure the quality of floor coatings.
How does DOI affect the use of 3M™ Trizact™ Diamond HX Discs and Scotchgard™ Floor Protectors?
One of the major benefits of using 3M™ Trizact™ Diamond HX Discs prior to the application of a floor coating is a dramatic increase in DOI. Because Scotchgard™ Stone Floor Protector is applied thin, it does not "orange peel" and is able to maintain the smoothness and DOI of the Trizact™ Diamond HX Disc prepared flooring, while enhancing the gloss. Floors that have similar traditional gloss readings will have a better perceived appearance with the increased DOI provided by use of 3M™ Trizact™ Diamond HX Discs than those without. The following two images are provided to demonstrate the enhanced appearance of surfaces with similar gloss and different DOI values.